Question

How do you balance $HCl+Ca{{(OH)}_{2}}\to {{H}_{2}}O+CaC{{l}_{2}}$?

Answer 1

Hint: The law of conservation of mass attributes for balancing a chemical equation. In a balanced chemical equation the number of particular elements in a reactant should be equal to the number of elements in the product.

Complete answer:
Firstly it is very important to know the law of conservation of mass which states that the atoms are neither created nor destroyed. In a chemical equation the substance that is left to the arrow is called reactant and the substance that is to the right of the arrow is called product. Applying the law of conservation of mass to a chemical, there is no atom destroyed from the reactant side nor created in the product, so the number of elements in the reactant is equal to the number of elements in the product. This is the theory behind balancing chemical equations.
Let's try a trial and error method, where we will check if the number of elements in the reactant is equal to the number of elements in the product and balance the given chemical equation.
 \[HCl+Ca{{(OH)}_{2}}\to {{H}_{2}}O+CaC{{l}_{2}}\]
-The number of H atoms in the reactant is 3 but in product there are only 2 H atoms. So, let's add 2 before HCl and ${{H}_{2}}O$ in order to balance the number of H atoms in the above written chemical equation.
\[2HCl+Ca{{(OH)}_{2}}\to 2{{H}_{2}}O+CaC{{l}_{2}}\]……………….equation 1
Now, the number of H atoms is 4 on both sides. The number of Ca , O and Cl atoms on both sides are equal. Thus, equation 1 is the balanced chemical equation of a given chemical equation.

Note:
Chemical equation is the representation of a chemical reaction where the reactants react to give products. One simple principle of balancing chemical equations is that the number of a particular element in the reactant should be equal to the number of elements in the product.